Expandable laser catheter

ABSTRACT

Expandable laser catheters for utilizing laser energy to remove obstructions from body passages are described. In one embodiment, the laser catheter includes a shaftway having a distal end including a flexible portion configured in a series of radial folds. Multiple optical fibers, configured to transmit laser energy, extend along the shaftway and are attached to the flexible portion. An inflatable, ring-shaped balloon is attached to the catheter within the flexible portion. In use, the catheter is inserted into a body passage such as an artery, and advanced until the distal end is adjacent to an obstruction. The balloon is inflated to expand the flexible portion and to bring the optical fibers nearer the inner wall of the body passage. Laser energy is directed by the optical fibers toward targeted regions of the obstruction, As the catheter is advanced and the process repeated, a core is formed from the obstruction and contained within the flexible portion. The flexible portion is then contracted to hold the core, and the core is removed from the body passage by withdrawing the catheter.

FIELD OF THE INVENTION

This invention relates generally to laser catheters and moreparticularly, to an expandable laser catheter for removing obstructionsfrom body passages.

BACKGROUND OF THE INVENTION

Atherosclerotic plaque is known to build up on the walls of arteries inthe human body. Such plaque build-up restricts circulation and oftencauses cardiovascular problems, especially when the build-up occurs incoronary arteries. Other body passages such as the esophagus, ureter andbile ducts, for example, are subject to blockage by tumorous tissue.Accordingly, it is desirable to remove or otherwise reduce plaquebuild-up and other tissue obstructions from such body passages.

Known catheters use laser energy to remove plaque build-up on arterywalls. One such known catheter has a laser source and a catheter body.The catheter body has a proximal end and a distal end, or head, andmultiple optical fibers extending between the proximal and distal ends.The laser source is coupled to the optical fibers at the proximal end ofthe catheter body and is configured to transmit laser energy through theoptical fibers.

To remove an obstruction from a body passage, such as atheroscleroticplaque in an artery, the catheter is positioned in the artery so thatthe distal end of the catheter is adjacent to the plaque. The lasersource is then energized so that laser energy travels through theoptical fibers and photoablates the plaque adjacent the distal end ofthe catheter. The catheter is then advanced further through the arteryto photoablate the next region of plaque build-up.

While known laser catheters are generally acceptable for removing smallobstructions, such catheters are limited to opening a path the size ofthe catheter head on each pass through the body passage. The multiplepasses which are required for removing larger areas of obstructionincrease the possibility of damaging the passage inner wall. Inaddition, multiple passes increase the possibility that a piece of theobstruction will break free, enter the blood stream and result in vesselblockage. Other known laser catheters are limited by the relativeinflexibility of the catheter distal end which may inflict damage tobody passage inner walls as the catheter is advanced.

Accordingly it would be desirable to provide a laser catheter which canremove substantial portions of an obstruction in a single pass. It wouldalso be desirable to provide a laser catheter having a flexible,adjustable distal end which can substantially conform to the innerdimensions of the body passageway to minimize damage to the inner wall.It would be further desirable to provide a laser catheter which canexpand and contract during photoablation to increase the area ofobstruction which may be photoablated in a single pass through a bodypassage.

SUMMARY OF THE INVENTION

These and other objects may be attained by a laser catheter which, inone embodiment, includes a shaftway having a proximal end and a distalend including a flexible portion. The flexible portion is fabricatedfrom a pliable material and is configured in folds which are radiallyoriented about the longitudinal axis of the catheter. The flexibleportion is configured to be expanded by, for example, an inflatableballoon which is attached within the flexible portion. Optical fibersextend along the length of the catheter to transmit laser energy fromthe proximal end to the distal end of the catheter, and are attached tothe catheter at the distal end. The ends of the optical fibers, at theirattachments to the distal end, are directed toward targeted regions ofan obstruction.

In use, a guidewire is inserted into a body passage such as an arteryand advanced past the obstruction. The catheter is then advanced overthe guidewire through the artery until the distal end of the catheter isadjacent to the obstruction, such as atherosclerotic plaque. The balloonis then inflated to expand the flexible portion of the distal end. Uponexpansion, the flexible portion substantially conforms to the innerdimensions of the body passage and is enlarged so that the flexibleportion can hold a core of material from the obstruction. A laserconnected to the optical fibers at the catheter proximal end is thenenergized, and the laser energy transmitted through the optical fibersphotoablates the obstruction in the regions targeted by the opticalfibers. The catheter is then advanced and the process repeated.

As the catheter is advanced and targeted regions photoablated, thecatheter detaches a separate core of material from the obstruction. Asthe core is formed the catheter advances over the core so thatultimately the core is completely contained within the flexible portion.To remove the core of the obstruction, the balloon is deflated and theflexible portion contracts and holds the core of the obstruction. Thecatheter is then withdrawn from the body passage to remove the core ofthe obstruction from the body passage.

In an alternative embodiment, the laser catheter utilizes mechanicalspring force to expand the distal end of the laser catheter. In thisalternative embodiment, the optical fibers are attached to a stiffshaftway. A fin structure including a plurality of fins fabricated froma spring material is attached to the distal end of the shaftway. Thestiff shaftway is capable of transmitting torque to the distal end sothat the fin structure can be rotated, thus facilitating advancement ofthe fin structure, and complete removal of the obstruction. The finshave a substantially rolled shape and are expandable from a retractedposition to an extended position. In both the retracted position and theextended position the fins retain, a substantially rolled shape whichsubstantially conforms to the inner dimensions of the body passage, tominimize damage to the inner wall of the body passage. At the finstructure the ends of the optical fibers are attached and spread acrossthe fins and are directed parallel to the shaftway. The laser catheterfurther includes an outer catheter body or sheath slidably disposed overthe shaftway to retain the fin structure in the retracted position.

In use of the alternative embodiment, a guide wire is introduced into abody passage and advanced past the obstruction. The laser catheter isintroduced over the guide wire and advanced toward the obstruction. Whenthe distal end of the catheter is adjacent the obstruction, the shaftwayis rotated and advanced so that the fin structure is pushed out of theouter catheter body, thus releasing the fins from the retracted positionand allowing them to expand to the extended position. In the extendedposition, the fins contact the passage inner wall and the ends of theoptical fibers are directed parallel to the inner wall of the passage.The fin structure can be further advanced along the passage wall byadvancing the shaftway and sliding the fin structure along the passagewall. Laser energy is used to photoablate regions of the obstructiontargeted by the optical fibers. The mounting of the optical fibers onthe fin structure allows the obstruction to be removed from around thepassage central axis (around the guide wire) to the outside diameter ofthe passage, with the fins protecting normal passage inner wall fromphotoablation. When the obstruction has been removed, the fin structureis rotated and pulled back into the outer catheter body, thus causingthe fins to retract to the retracted position. The catheter is thenremoved from the body passage.

In additional alternative embodiments especially useful for openingin-stent restenosis, laser energy may be directed radially outward fromthe shaftway instead of parallel to the shaftway. This may beaccomplished by attaching the ends of the optical fibers at the finstructure so that the ends of the fibers are directed radially outwardfrom the shaftway, or alternatively, by coupling prisms to the ends ofthe optical fibers at the fin structure to direct laser energy radiallyoutwards from the shaftway.

The above described laser catheter removes substantial portions of anobstruction in a single pass by expanding the distal end of the catheterto substantially conform to the inner dimensions of the body passage.The laser catheter further minimizes damage to the body passage innerwall with a flexible, adjustable distal end. Further, the laser cathetermay be expanded and contracted during photoablation to increase the areaof obstruction which may be photoablated in a single pass. By removingsubstantial portions of an obstruction in a single pass, the lasercatheter obviates the need for multiple and potentially damaging passesthrough the body passage.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional view of a laser catheter.

FIG. 2 is a cross-sectional view of a distal end of the laser catheter.FIG. 3 is a sectional view of the distal end of the laser catheterpositioned adjacent to an obstruction in a body passage.

FIG. 4 is a sectional view of the catheter distal end within a bodypassage after expansion of the flexible portion and partialphotoablation of the obstruction.

FIG. 5 is a cross-sectional view of the catheter distal end within abody passage after expansion of the flexible portion and partialphotoablation of the obstruction.

FIG. 6 is a sectional view of the catheter distal end after formation ofa core of obstruction and contraction of the flexible portion.

FIG. 7 is a cross-sectional view of the catheter distal end afterformation of the core of obstruction and contraction of the flexibleportion.

FIG. 8 is a perspective view of a distal end of a laser catheter.

FIG. 9 is a cross-sectional view of the catheter distal end shown inFIG. 8 and positioned within a body passage.

FIG. 10 is a sectional view of the catheter distal end shown in FIG. 8and positioned within the body passage.

DETAILED DESCRIPTION

FIG. 1 is a sectional view of a laser catheter 10 in accordance with oneembodiment of the present invention. Catheter 10 includes a shaftway 12which defines a lumen 14 about a longitudinal axis, and has a proximalend 16, a distal end 18, and a flexible portion 20 adjacent distal end18. Flexible portion 20 is configured in a plurality of folds having aradial orientation about the longitudinal axis of lumen 14. Aring-shaped inflatable balloon 22, or other means for expanding flexibleportion 20, is attached to shaftway 12 within flexible portion 20.Balloon 20 may instead be attached to the guide wire or a mechanicaldevice. Catheter 10 extends over a conventional guidewire 24. Balloon 22is positioned from about 1 mm to about 10 mm behind the end of flexibleportion 20. Balloon 22 communicates via air lines or tubing (not shown)as known in the art to a means for inflating the balloon, such as asyringe, air compressor or other air pressure providing device (notshown). Multiple optical fibers (not shown in FIG. 1) extendlongitudinally along the length of catheter 10.

In one embodiment, shaftway 12 is approximately 80 to 150 cm long and isfabricated from conventional catheter materials such as, for example,polyurethane. Lumen 14 has a diameter of approximately 1 to 5 mm, andthe outer diameter of shaftway 12 is approximately 1.5 to 6 mm. Flexibleportion 20 is approximately 2 to 5 cm long and is fabricated from apliable material such as, for example, polyurethane. In the foldedconfiguration, the outer diameter of flexible portion 20 isapproximately the same size as the outer diameter of shaftway 12. In oneembodiment, flexible portion 20 is bonded to shaftway 12 by thermalfusion or an adhesive.

Referring to FIG. 2, catheter 10 includes multiple optical fibers 30.Fibers 30 extend longitudinally along the length of shaftway 12 intoflexible portion 20, and are attached to flexible portion 20. Fibers 30are of a type known in the art of laser catheters and are configured totransmit laser energy. In one embodiment, optical fibers 30 extendthrough lumen 14 and are embedded in the pliable material formingflexible portion 20. Optical fibers 30 have proximal ends (not shown)which are configured to connect through an optical fiber port (notshown) to a laser connector and a laser (not shown), such as an excimerlaser, Nd:YAG, holmium or CO2 laser. In one embodiment, the laser isconfigured to produce laser energy of a wavelength of about 0.3 micronsto about 2.0 microns. The composition of optical fibers 30 depends uponthe chosen laser and the wavelength of laser energy that the laserproduces. In one embodiment, the laser is an excimer laser producingenergy of a wavelength of about 0.3 microns, requiring optical fibersmade of quartz.

FIG. 3 is a sectional view of catheter 10 in use within a body passage34. In use, guidewire 24 is inserted into body passage 34 and advancedpast an obstruction 36. Catheter 10 is then inserted into body passage34 over guidewire 24 and advanced until distal end 18 is adjacentobstruction 36. Specifically, catheter 10 is advanced until distal end18 is positioned to contact obstruction 32 or to be within about 2 mm ofobstruction 32. The relative distance of distal end 18 to obstruction 36is determined using radiopaque markers and fluoroscopy, or other imagingtechniques known in the art. After flexible portion 20 is correctlypositioned adjacent obstruction 36, balloon 22 is inflated by applyingair pressure through tubing connecting balloon 22 with, for example, asyringe. Expansion of balloon 22 causes the flexible portion 20 toexpand in the radial dimension as the folds are unfolded creating a coreretention portion 38 within flexible portion 20. Balloon 22 is expandeduntil flexible portion 20 is adjacent to the inner wall of body passage34, as determined in one embodiment by a fluoroscopy image. The laser isenergized so that laser energy travels through fibers 30 to photoablateregions of obstruction 36.

Referring to FIGS. 4 and 5, flexible portion 20 is then advanced furtherthrough obstruction 36 and the process is repeated. Specifically asshown in FIG. 5, the end faces of optical fibers 30 in expanded flexibleportion 20 are positioned to direct laser energy toward regions ofobstruction 32 which approach or meet the inner wall of passage 30.

Referring to FIG. 6, catheter 10 photoablates regions of obstruction 36.Catheter 10 is then advanced further along passage 30. A core 50 ofmaterial from obstruction 36 is formed as catheter 10 photoablatesregions of obstruction 36 and is advanced. If catheter 10 is advancedthrough entire obstruction 36, or if the entire length of flexibleportion 20 is advanced through obstruction 36, air pressure is removedfrom balloon 22. As a result, flexible portion 20 contracts and retainscore 50 within core retention portion 38. More particularly, as balloon22 is deflated and flexible portion 20 contracts, core 50 is retainedwithin the folds of flexible portion 20. Core 50 is then removed frombody passage 34 by withdrawing catheter 10 from body passage 34. FIG. 7is a cross-sectional view of contracted flexible portion 20 within bodypassage 34, retaining core 50 after core 50 has been formed.

In an alternative embodiment of the method, obstruction 36 is entirelyor substantially removed from body passage 34 by photoablation. Balloon22 is expanded and contracted to impart radial motion to fibers 30during photoablation, thereby increasing the area of obstruction 36which is exposed to laser energy on a single pass through body passage34. In addition, shaftway 12 may be rotated to impart tangential motionto fibers 30 to further facilitate substantial photoablation ofobstruction 36.

In another alternative embodiment of catheter 10, shaftway 12 may beslidably inserted through an outer catheter body (not shown) to providerigidity to flexible portion 20 as flexible portion 20 is advancedthrough body passage 34. Catheter 10 is advanced through body passage 34until flexible portion 20 is within a defined distance of obstruction 36as defined above. Flexible portion 20 is then extended out of the outercatheter body and is free to expand. Alternatively, the outer catheterbody may be partially retracted to free flexible portion 20. Afterexpansion of flexible portion 20, photoablation and formation of core50, flexible portion 20 retaining core 50 is retracted within the outercatheter body and catheter 10 is withdrawn from body passage 34.

In an alternate embodiment shown in FIG. 8, catheter 60 utilizesmechanical spring force to expand the distal end of the laser catheter.Catheter 60 includes a stiff shaftway 62 having a proximal end (notshown) and a distal end 64. A fin structure including fins 66A and 66Bis attached to distal end 64. Fins 66A and 66B extend from shaftway 62and are configured to have a retracted position (not shown) and anextended position (shown in FIG. 8). Stiff shaftway 62 is capable oftransmitting torque to the distal end and allows the fin structure to berotated to facilitate advancement of the fin structure, and completeremoval of the obstruction. Fins 66A and 66B have a substantially rolledshape in both the retracted position and the extended position, allowingfins 66A and 66B to substantially conform to the inner dimensions of thebody passage, to minimize damage to the inner wall of the body passage.Optical fibers 68, similar to optical fibers 30, extend from theproximal end to distal end 64 and are attached and spread across tins66A and 66B. Proximal ends of optical fibers 68 (not shown) may beconfigured to connect through an optical fiber port (not shown) to alaser connector and a laser (not shown), such as an excimer laser,Nd:YAG, holmium or CO2 laser. Shaftway 62 is slidably positioned withinan outer catheter body 70 which is configured to retain fins 66A and 66Bin the retracted position. Shaftway 62 slidably extends over guidewire72, which is similar to guidewire 24.

In one embodiment, shaftway 62 is fabricated from conventional cathetermaterials such as, for example, stainless steel hypodermic tubing. Fins66A and 66B are fabricated from a spring material such as a metal alloyfoil. In one embodiment, the foils generally have a thickness of about0.001 inches and may be fabricated from, for example, stainless steel,niatinol or precipitation hardened steel. Thus, fins 66A and 66B expandfrom the retracted rolled shape to the extended rolled shape due to themechanical spring force of the foil. Fins 66A and 66B are attached toshaftway 62 by welding or brazing, are about 10 to about 30 mm long, andextend about 1.5 mm to about 15 mm from their attachments at shaftway62. Outer catheter body 70 is fabricated from conventional cathetermaterials as known in the art.

In one embodiment, distal end 64 includes two fins 66A and 66B, but anynumber of fins may be used. Distal ends of optical fibers 68 areattached to the spring material forming fins 66A and 66B so that theends of optical fibers 68 are at an angle, or parallel, to the centralaxis of the body passage. For example, the distal ends of optical fibers68 may be directed in any desired direction from parallel to the centralaxis of the body passage, to perpendicular to the inner wall of the bodypassage. The desired direction is determined by the size and shape ofthe obstruction to be excised. For example, it is particularly desirableto aim fiber ends at a substantial angle, including substantiallyperpendicularly, to the body passage inner wall for photoablation ofwell-defined regions of obstruction, such as restenosis within a stent.

FIG. 9 is a cross-sectional view of distal end 64 positioned within abody passage 96 and adjacent to an obstruction 98. Distal end 64 isshown extending beyond outer catheter body 70. Fins 66A and 66B are inthe extended position. FIG. 10 is a sectional view of distal end 64 withfins 66A and 66B in the extended position as shown in FIG. 9. In oneembodiment, fins 66A and 66B each have a leading edge 100, a trailingedge 102, and a peripheral edge 104. To facilitate navigation of distalend 64 through curves in body passage 96, fins 66A and 66B are taperedalong leading edge 100 and trailing edge 102 so that fins 66A and 66Bare widest at their attachments to shaftway 62 and shortest alongperipheral edge 104.

In use, guidewire 72 is inserted into body passage 96 and advanced pastobstruction 98. Catheter 60 is then inserted into body passage 96 overguidewire 72. Fins 66A and 66B are retained in the retracted positionwithin outer catheter body 70. Catheter 60 is advanced within passage 96until distal end 64 is positioned proximate obstruction 98, for example,within about 2 mm. Distal end 64 is extended out of outer catheter body70 by advancing shaftway 62, thereby releasing the restraint on fins 66and allowing fins 66 to extend and conform to the inner dimensions ofbody passage 96. The laser coupled to the proximate ends of opticalfibers 68 is energized so that laser energy travels through fibers 68 tophotoablate regions of obstruction 98. Distal end 64 may be rotated andadvanced further along passage 96 for photoablation of any remainingregions of obstruction 98. The spring material forming fins 66A and 66Bprotects against damage to the passage inner wall by preventing directcontact by optical fibers 68 with the inner wall. Once obstruction 98has been photoablated, distal end 64 is pulled back into outer catheterbody 70 to retract fins 66A and 66B and facilitate removal from bodypassage 96.

Alternate embodiments of the laser catheters described herein may beused to remove small or large regions of atherosclerotic plaque fromblocked blood vessels, or regions of tumor invading an esophagus,ureter, urethra, bile duct or other body passage. The catheters may alsobe used, for example, to aid in the removal of excess or abnormalcartilage in body joints such as knees, or in disc spaces betweenvertebral bodies. The catheters may be used without guidewires andinstead with alternate guidance methods such as optical coherencetomography (OCT), ultrasound, CT scanning or fluoroscopy. The cathetersmay be surgically introduced to body passages or elsewhere in the bodyusing known instruments such as arthroscopes, endoscopes, colonoscopes,bronchoscopes, laparoscopes, etc. The distal end faces of the opticalfibers may be rounded, or square-cut, cut at an angle, or connected toan optical prism lens to more precisely target certain regions of theobstruction. To further minimize damage to the body passage inner wall,the flexible portion substantially conforms to the inner dimensions ofthe body passage. In an alternate method of use, the flexible portion isexpanded and contracted during photoablation to increase the area ofobstruction which is removed by direct photoablation in one pass throughthe body passage.

The above described laser catheter improves the efficacy and safety ofusing laser energy to remove large areas of an obstruction from a bodypassage. The laser catheter of the present invention uses photoablationto create a core of an obstruction which is then removed as a singlemass at one time. The laser catheter therefore minimizes damage to bodypassage walls by obviating the need for multiple passes through the bodypassage. Alternate embodiments of the method for using the lasercatheter include expanding and contracting the flexible distal portionduring photoablation of the obstruction, thereby photoablating largeareas of obstructions in one pass and minimizing damage to body passagewalls. In addition, the laser catheter includes a distal end whichsubstantially conforms to the inner dimensions of the body passagewayand further minimizes damage to body passage inner walls.

From the preceding description of various embodiments of the presentinvention, it is evident that the objects of the invention are attained.Although the invention has been described and illustrated in detail, itis to be clearly understood that the same is intended by way ofillustration and example only and is not to be taken by way oflimitation. Accordingly, the spirit and scope of the invention are to belimited only by the terms of the appended claims.

What is claimed is: 1-35. (canceled)
 36. A method for using a catheterto photoablate an obstruction from a body passage, the catheterincluding a shaftway defining a lumen extending therethrough, theshaftway comprising a proximal end and a distal end, the catheterfurther comprising a flexible portion adjacent the distal end of theshaftway, the flexible portion comprising at least one expandable membermechanically attached to the shaftway and extending radially therefrom,a balloon for expanding the at least one expandable member, and aplurality of optical fibers each having a distal end attached to theexpandable member, the method comprising the steps of: inserting thecatheter into the body passage; advancing the catheter until thecatheter is adjacent to the obstruction; expanding the at least oneexpandable member by inflating the balloon; photoablating theobstruction by transmitting laser energy through the plurality ofoptical fibers; forming a core of the obstruction within the flexibleportion by advancing the catheter while photoablating the obstruction;and containing the core of the obstruction within the flexible portionby contracting the at least one expandable member.
 37. The method ofclaim 36, wherein contracting the at least one expandable membercomprises contracting the at least one expandable member by deflatingthe balloon.
 38. The method of claim 37, further comprising impartingradial motion to the plurality of optical fibers by inflating anddeflating the balloon while photoablating the obstruction.
 39. Themethod of claim 36, further comprising rotating the optical fibers byrotating the shaftway.
 40. The method of claim 39, further comprisingrotating the shaftway while photoablating the obstruction.